LONDON (Reuters) - Dealmaking in the United States has made its strongest start to a year since Reuters records began in 1980, climbing 52 percent year on year to $746.9 billion in the Jan. 1 to May 28 period.

Merger and acquisition (M&A) activity was boosted this week when Charter Communications (CHTR.O) said it would acquire larger rival Time Warner Cable (TWC.N) for $56 billion and Avago Technologies (AVGO.O) agreed to buy rival chipmaker Broadcom Corp (BRCM.O) for $37 billion.

The Time Warner deal also propelled cable M&A up 42 percent year on year to $97.2 billion.

Morgan Stanley (MS.N), which advised Time Warner Cable on its second approach from Charter Communications, along with Citi (C.N), Allen & Co and Centerview, tops the list of U.S. M&A advisers.

Global M&A activity is up 35 percent from the same period in 2014, with $1.7 trillion of deals having been struck.

(For more weekly data click here: http://trmcs-documents.s3.amazonaws.com/3501ec8eae589bfbef9cc1729a7312f0_20150529081343_IB%20Scorecard%20Weekly%20Highlights_052815.pdf

For data on year-to-date investment banking activity click here: http://trmcs-documents.s3.amazonaws.com/3501ec8eae589bfbef9cc1729a7312f0_20150529081344_Weekly%20Scorecard%20Template%20052815.pdf)

(Reporting By Anjuli Davies; Editing by David Goodman)